United Launch Alliance’s powerful new Vulcan rocket was originally scheduled to debut in 2020 but has since been delayed a couple of times.

Presently, it is due to fly during the second half of this year, and the Colorado-based launch company is still holding to the 2022 date. On Wednesday, United Launch Alliance spokesperson Jessica Rye told Ars, “We are well positioned for a Vulcan first launch late this year.” However, another delay now seems inevitable, sources say, with the rocket slipping toward a demonstration launch in 2023.

There are two main issues holding Vulcan back from making its debut: the readiness of its main engines and the payload that it will carry. At this point, neither appear likely to support a 2022 launch.